I don't even watch Dr. Who. I've seen a few episodes, but sci-fi is rarely my genre of choice, and for me it falls into the category of "I can see why people love this; I just don't personally feel that invested."
I feel invested now. And I hope you'll forgive an outsider's weighing in; I have little experience with this show, but lots of experience with being influenced by fictional and fictionalized characters.
Like the moment in college when I first saw the movie Dogma (spoiler ahead). God, or God's corporeal form, is portrayed in that movie by a long-haired, twenty-something Alanis Morissette. Somewhere around the part where she does ungainly but joyful handstands among the flowers, I remember thinking to myself, "If she can be an all-powerful being, I can handle writing my English 221 paper."
Yes, this was a silly thought. But the fact that I had it means that, after about nineteen years of life, the idea of a woman having that much power was new to me, and mattered. Maybe we should be past the point where casting a woman as the powerful one is no big deal, but we're not there yet. We still need to put more powerful women, and powerful people of color, and powerful people outside the default into our movies, TV shows, and books. Especially the books that are going to end up in young people's hands.
Good job, Dr. Who. It's about time.